<<  <  Page 3/3
Dave Palmer
User Rank
Re: Commonplace Chemicals
Dave Palmer   2/3/2012 11:50:24 AM
@Alex: When it comes to environmental stress cracking, there is not necessarily any advantage to making the plastic thicker or thinner.  The key variables are stress and chemical exposure.  If by making the plastic thicker, you can reduce the stress below the threshold, then it might be a solution.  But often the threshold stress is so low that this is impractical.  And if the internal stresses in the material are high enough, it doesn't matter what you do with the external stress.

Here is a good introduction to residual stress in plastics.  At some risk of oversimplification, thin-wall sections are more likely to have flow-induced residual stresses, while thick-wall sections are more likely to have thermal-induced residual stresses.  But either way, molded-in stresses can be significant.

Alexander Wolfe
User Rank
Commonplace Chemicals
Alexander Wolfe   2/3/2012 11:16:41 AM
I never realized the commonplace chemicals like oil and grease were precursors to stress cracking in plastics. Good to know. Also didn't realize there's some built-in prestress. It seems that, in consumer systems, the plastic always ends up cracking at some point. Is that because thin(ner) plastics are always prone to cracking (and on the other side of the design equation, making them thick enough to be more crack resistant doesn't comport with weight and cost requirements. Or are the thicker plastics just as stress-crack prone?)

<<  <  Page 3/3

Partner Zone
Latest Analysis
Do you wear your ugly Christmas sweater while fighting zombies, or simply chill in front of your homemade entertainment center while your automated cat feeder keeps your feline friend at bay? Whatever you prefer, one of the following gadgets is sure to get your DIY motor running.
The design of products has been altered altogether through 3D printing. Parts that couldn’t be produced at all before 3D printing came along are often superior to conventionally produced parts.
Marine mussels and their interaction with the ocean environment has inspired a breakthrough in developing a nontoxic coating for organic electronic components that also could speed up the manufacturing process.
The Innovation Challenge Awards had one run-away winner at ARM TechCon 2016. Of the six awards presented, one company walked away with four.
Clearly, zombies are in this year -- taking over from a decade of vampire dominance in Halloween fashion.
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Oct 10 - 14, Embedded System Design Techniques™: Getting Started Developing Professional Embedded Software
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7 | 8 | 9 | 10

Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Course November 8 - 10:
Sponsored by 3M
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Technology Marketplace

Copyright © 2016 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service